1. Field of the Invention
The present invention relates to a group III nitride compound semiconductor light-emitting device of high light intensity.
The present application is based on Japanese Patent Application No. Hei. 11-90719, which is incorporated herein by reference.
2. Description of the Related Art
FIG. 2 is a sectional view showing a structure of a group III nitride compound semiconductor light-emitting device 200 according to related art.
The group III nitride compound semiconductor light-emitting device 200 is representative of light-emitting devices of the type having layers of group III nitride semiconductors laminated on a substrate.
The group III nitride compound semiconductor light-emitting device 200 comprises a sapphire substrate 11 as a substrate, a buffer layer 12 of aluminum nitride (AlN) laminated on the sapphire substrate 11, an n+ layer 13 of a high carrier density formed of GaN doped with silicon (Si) and laminated on the buffer layer 12, an intermediate layer 14 laminated on the n+ layer 13, an n-type clad layer 15 of GaN laminated on the intermediate layer 14, a light-emitting layer 16 of a multilayer quantum well structure (MQW) laminated on the n-type clad layer 15 and composed of alternately laminated well layers 161 of GaInN and barrier layers 162 of GaN, a p-type clad layer 18 of p-type AlGaN laminated on the p-type clad layer, and a p-type contact layer 19 of p-type GaN laminated on the p-type clad layer.
In the aforementioned light-emitting device 200, the barrier layers 162 are made substantially uniform in thickness so as to be generally in a range of 70 to 80 Å. Moreover, from the point of view of improvement in color purity, the intermediate layer 14 of InGaN is provided, and the n-type clad layer 15 having the same thickness and composition as each of the barrier layers 162 is also formed.
In the group III nitride compound semiconductor light-emitting device such as the aforementioned light-emitting device 200, or the like, there is a problem in that the effect of confining carriers in the light-emitting layer 16 against the high carrier density n+ layer 13 is unable to be obtained sufficiently because the thickness of the n-type clad layer 15 under the light-emitting layer 16 is substantially equal to the thickness of each of the barrier layers 162, and therefore light-emitting efficiency is low in spite of very good color purity.